Controle optique de microgouttes

Abstract : One of the most important objectives of microfluidics is the development of laboratories on a chip (LOC), whose but is the construction of microchannels that are able to contain and automate the analytical work in biology or chemistry. In this technology, drops constitute attractive reaction chambers to contain the reagents of an analysis. The success of droplet based LOC relies in the development of techniques for the manipulation of drops. The objective of this thesis is the development of a technique to manipulate microdrops with a focused laser beam. In particular, this technique uses the laser heating to modify the flows by changing the physical properties of the fluids. In the case of a single drop, the heating induces a surface tension gradient, which creates a thermocapillary flow both inside and outside the drop. These flows originate a force that pushes the drop away from the laser beam. In a first part, this thesis shows the physical mechanisms below the establishment of this force and uses it to sort drops and store drops in an external flow. In a second part, the thermocapillary flows are temporally modulated to achieve the mixing of the drop contents in a drop held by the laser forcing. The laser heating is finally used to trigger the drop formation in a co-flow geometry. In this geometry, one liquid is injected inside an external liquid, both fluid flowing in parallel. The inner liquid forms a thread that breaks up into drops of disperse size. The laser, whse power is sinusoidally modulated, is used to modify the viscosity of the inner liquid, thus locally destabilizing the flow. This allows the control on the drop formation frequency and therefore on the drop size as a function of the laser frequency.
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Theses
Engineering Sciences. Ecole Polytechnique X, 2009. English


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Submitted on : Wednesday, July 7, 2010 - 8:00:00 AM
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  • HAL Id : pastel-00005646, version 1

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Maria Luisa Cordero. Controle optique de microgouttes. Engineering Sciences. Ecole Polytechnique X, 2009. English. <pastel-00005646>

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